src/hotspot/share/gc/cms/compactibleFreeListSpace.hpp
changeset 59193 b83adf4bd4ee
parent 59192 a56b7a304bac
parent 59142 c4be5e03aff7
child 59194 10385df5d986
equal deleted inserted replaced
59192:a56b7a304bac 59193:b83adf4bd4ee
     1 /*
       
     2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
       
     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
       
     4  *
       
     5  * This code is free software; you can redistribute it and/or modify it
       
     6  * under the terms of the GNU General Public License version 2 only, as
       
     7  * published by the Free Software Foundation.
       
     8  *
       
     9  * This code is distributed in the hope that it will be useful, but WITHOUT
       
    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
       
    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
       
    12  * version 2 for more details (a copy is included in the LICENSE file that
       
    13  * accompanied this code).
       
    14  *
       
    15  * You should have received a copy of the GNU General Public License version
       
    16  * 2 along with this work; if not, write to the Free Software Foundation,
       
    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
       
    18  *
       
    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
       
    20  * or visit www.oracle.com if you need additional information or have any
       
    21  * questions.
       
    22  *
       
    23  */
       
    24 
       
    25 #ifndef SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP
       
    26 #define SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP
       
    27 
       
    28 #include "gc/cms/adaptiveFreeList.hpp"
       
    29 #include "gc/cms/promotionInfo.hpp"
       
    30 #include "gc/shared/blockOffsetTable.hpp"
       
    31 #include "gc/shared/cardTable.hpp"
       
    32 #include "gc/shared/space.hpp"
       
    33 #include "logging/log.hpp"
       
    34 #include "memory/binaryTreeDictionary.hpp"
       
    35 #include "memory/freeList.hpp"
       
    36 
       
    37 // Classes in support of keeping track of promotions into a non-Contiguous
       
    38 // space, in this case a CompactibleFreeListSpace.
       
    39 
       
    40 // Forward declarations
       
    41 class CMSCollector;
       
    42 class CompactibleFreeListSpace;
       
    43 class ConcurrentMarkSweepGeneration;
       
    44 class BlkClosure;
       
    45 class BlkClosureCareful;
       
    46 class FreeChunk;
       
    47 class UpwardsObjectClosure;
       
    48 class ObjectClosureCareful;
       
    49 class Klass;
       
    50 
       
    51 class AFLBinaryTreeDictionary : public BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> > {
       
    52  public:
       
    53   AFLBinaryTreeDictionary(MemRegion mr)
       
    54       : BinaryTreeDictionary<FreeChunk, AdaptiveFreeList<FreeChunk> >(mr) {}
       
    55 
       
    56   // Find the list with size "size" in the binary tree and update
       
    57   // the statistics in the list according to "split" (chunk was
       
    58   // split or coalesce) and "birth" (chunk was added or removed).
       
    59   void       dict_census_update(size_t size, bool split, bool birth);
       
    60   // Return true if the dictionary is overpopulated (more chunks of
       
    61   // this size than desired) for size "size".
       
    62   bool       coal_dict_over_populated(size_t size);
       
    63   // Methods called at the beginning of a sweep to prepare the
       
    64   // statistics for the sweep.
       
    65   void       begin_sweep_dict_census(double coalSurplusPercent,
       
    66                                      float inter_sweep_current,
       
    67                                      float inter_sweep_estimate,
       
    68                                      float intra_sweep_estimate);
       
    69   // Methods called after the end of a sweep to modify the
       
    70   // statistics for the sweep.
       
    71   void       end_sweep_dict_census(double splitSurplusPercent);
       
    72   // Accessors for statistics
       
    73   void       set_tree_surplus(double splitSurplusPercent);
       
    74   void       set_tree_hints(void);
       
    75   // Reset statistics for all the lists in the tree.
       
    76   void       clear_tree_census(void);
       
    77   // Print the statistics for all the lists in the tree.  Also may
       
    78   // print out summaries.
       
    79   void       print_dict_census(outputStream* st) const;
       
    80 };
       
    81 
       
    82 class LinearAllocBlock {
       
    83  public:
       
    84   LinearAllocBlock() : _ptr(0), _word_size(0), _refillSize(0),
       
    85     _allocation_size_limit(0) {}
       
    86   void set(HeapWord* ptr, size_t word_size, size_t refill_size,
       
    87     size_t allocation_size_limit) {
       
    88     _ptr = ptr;
       
    89     _word_size = word_size;
       
    90     _refillSize = refill_size;
       
    91     _allocation_size_limit = allocation_size_limit;
       
    92   }
       
    93   HeapWord* _ptr;
       
    94   size_t    _word_size;
       
    95   size_t    _refillSize;
       
    96   size_t    _allocation_size_limit;  // Largest size that will be allocated
       
    97 
       
    98   void print_on(outputStream* st) const;
       
    99 };
       
   100 
       
   101 // Concrete subclass of CompactibleSpace that implements
       
   102 // a free list space, such as used in the concurrent mark sweep
       
   103 // generation.
       
   104 
       
   105 class CompactibleFreeListSpace: public CompactibleSpace {
       
   106   friend class VMStructs;
       
   107   friend class ConcurrentMarkSweepGeneration;
       
   108   friend class CMSCollector;
       
   109   // Local alloc buffer for promotion into this space.
       
   110   friend class CompactibleFreeListSpaceLAB;
       
   111   // Allow scan_and_* functions to call (private) overrides of the auxiliary functions on this class
       
   112   template <typename SpaceType>
       
   113   friend void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space);
       
   114   template <typename SpaceType>
       
   115   friend void CompactibleSpace::scan_and_compact(SpaceType* space);
       
   116   template <typename SpaceType>
       
   117   friend void CompactibleSpace::verify_up_to_first_dead(SpaceType* space);
       
   118   template <typename SpaceType>
       
   119   friend void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp);
       
   120 
       
   121   // "Size" of chunks of work (executed during parallel remark phases
       
   122   // of CMS collection); this probably belongs in CMSCollector, although
       
   123   // it's cached here because it's used in
       
   124   // initialize_sequential_subtasks_for_rescan() which modifies
       
   125   // par_seq_tasks which also lives in Space. XXX
       
   126   const size_t _rescan_task_size;
       
   127   const size_t _marking_task_size;
       
   128 
       
   129   // Yet another sequential tasks done structure. This supports
       
   130   // CMS GC, where we have threads dynamically
       
   131   // claiming sub-tasks from a larger parallel task.
       
   132   SequentialSubTasksDone _conc_par_seq_tasks;
       
   133 
       
   134   BlockOffsetArrayNonContigSpace _bt;
       
   135 
       
   136   CMSCollector* _collector;
       
   137   ConcurrentMarkSweepGeneration* _old_gen;
       
   138 
       
   139   // Data structures for free blocks (used during allocation/sweeping)
       
   140 
       
   141   // Allocation is done linearly from two different blocks depending on
       
   142   // whether the request is small or large, in an effort to reduce
       
   143   // fragmentation. We assume that any locking for allocation is done
       
   144   // by the containing generation. Thus, none of the methods in this
       
   145   // space are re-entrant.
       
   146   enum SomeConstants {
       
   147     SmallForLinearAlloc = 16,        // size < this then use _sLAB
       
   148     SmallForDictionary  = 257,       // size < this then use _indexedFreeList
       
   149     IndexSetSize        = SmallForDictionary  // keep this odd-sized
       
   150   };
       
   151   static size_t IndexSetStart;
       
   152   static size_t IndexSetStride;
       
   153   static size_t _min_chunk_size_in_bytes;
       
   154 
       
   155  private:
       
   156   enum FitStrategyOptions {
       
   157     FreeBlockStrategyNone = 0,
       
   158     FreeBlockBestFitFirst
       
   159   };
       
   160 
       
   161   PromotionInfo _promoInfo;
       
   162 
       
   163   // Helps to impose a global total order on freelistLock ranks;
       
   164   // assumes that CFLSpace's are allocated in global total order
       
   165   static int   _lockRank;
       
   166 
       
   167   // A lock protecting the free lists and free blocks;
       
   168   // mutable because of ubiquity of locking even for otherwise const methods
       
   169   mutable Mutex _freelistLock;
       
   170 
       
   171   // Locking verifier convenience function
       
   172   void assert_locked() const PRODUCT_RETURN;
       
   173   void assert_locked(const Mutex* lock) const PRODUCT_RETURN;
       
   174 
       
   175   // Linear allocation blocks
       
   176   LinearAllocBlock _smallLinearAllocBlock;
       
   177 
       
   178   AFLBinaryTreeDictionary* _dictionary;    // Pointer to dictionary for large size blocks
       
   179 
       
   180   // Indexed array for small size blocks
       
   181   AdaptiveFreeList<FreeChunk> _indexedFreeList[IndexSetSize];
       
   182 
       
   183   // Allocation strategy
       
   184   bool _fitStrategy;  // Use best fit strategy
       
   185 
       
   186   // This is an address close to the largest free chunk in the heap.
       
   187   // It is currently assumed to be at the end of the heap.  Free
       
   188   // chunks with addresses greater than nearLargestChunk are coalesced
       
   189   // in an effort to maintain a large chunk at the end of the heap.
       
   190   HeapWord*  _nearLargestChunk;
       
   191 
       
   192   // Used to keep track of limit of sweep for the space
       
   193   HeapWord* _sweep_limit;
       
   194 
       
   195   // Stable value of used().
       
   196   size_t _used_stable;
       
   197 
       
   198   // Used to make the young collector update the mod union table
       
   199   MemRegionClosure* _preconsumptionDirtyCardClosure;
       
   200 
       
   201   // Support for compacting cms
       
   202   HeapWord* cross_threshold(HeapWord* start, HeapWord* end);
       
   203   HeapWord* forward(oop q, size_t size, CompactPoint* cp, HeapWord* compact_top);
       
   204 
       
   205   // Initialization helpers.
       
   206   void initializeIndexedFreeListArray();
       
   207 
       
   208   // Extra stuff to manage promotion parallelism.
       
   209 
       
   210   // A lock protecting the dictionary during par promotion allocation.
       
   211   mutable Mutex _parDictionaryAllocLock;
       
   212   Mutex* parDictionaryAllocLock() const { return &_parDictionaryAllocLock; }
       
   213 
       
   214   // Locks protecting the exact lists during par promotion allocation.
       
   215   Mutex* _indexedFreeListParLocks[IndexSetSize];
       
   216 
       
   217   // Attempt to obtain up to "n" blocks of the size "word_sz" (which is
       
   218   // required to be smaller than "IndexSetSize".)  If successful,
       
   219   // adds them to "fl", which is required to be an empty free list.
       
   220   // If the count of "fl" is negative, it's absolute value indicates a
       
   221   // number of free chunks that had been previously "borrowed" from global
       
   222   // list of size "word_sz", and must now be decremented.
       
   223   void par_get_chunk_of_blocks(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
       
   224 
       
   225   // Used by par_get_chunk_of_blocks() for the chunks from the
       
   226   // indexed_free_lists.
       
   227   bool par_get_chunk_of_blocks_IFL(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
       
   228 
       
   229   // Used by par_get_chunk_of_blocks_dictionary() to get a chunk
       
   230   // evenly splittable into "n" "word_sz" chunks.  Returns that
       
   231   // evenly splittable chunk.  May split a larger chunk to get the
       
   232   // evenly splittable chunk.
       
   233   FreeChunk* get_n_way_chunk_to_split(size_t word_sz, size_t n);
       
   234 
       
   235   // Used by par_get_chunk_of_blocks() for the chunks from the
       
   236   // dictionary.
       
   237   void par_get_chunk_of_blocks_dictionary(size_t word_sz, size_t n, AdaptiveFreeList<FreeChunk>* fl);
       
   238 
       
   239   // Allocation helper functions
       
   240   // Allocate using a strategy that takes from the indexed free lists
       
   241   // first.  This allocation strategy assumes a companion sweeping
       
   242   // strategy that attempts to keep the needed number of chunks in each
       
   243   // indexed free lists.
       
   244   HeapWord* allocate_adaptive_freelists(size_t size);
       
   245 
       
   246   // Gets a chunk from the linear allocation block (LinAB).  If there
       
   247   // is not enough space in the LinAB, refills it.
       
   248   HeapWord*  getChunkFromLinearAllocBlock(LinearAllocBlock* blk, size_t size);
       
   249   HeapWord*  getChunkFromSmallLinearAllocBlock(size_t size);
       
   250   // Get a chunk from the space remaining in the linear allocation block.  Do
       
   251   // not attempt to refill if the space is not available, return NULL.  Do the
       
   252   // repairs on the linear allocation block as appropriate.
       
   253   HeapWord*  getChunkFromLinearAllocBlockRemainder(LinearAllocBlock* blk, size_t size);
       
   254   inline HeapWord*  getChunkFromSmallLinearAllocBlockRemainder(size_t size);
       
   255 
       
   256   // Helper function for getChunkFromIndexedFreeList.
       
   257   // Replenish the indexed free list for this "size".  Do not take from an
       
   258   // underpopulated size.
       
   259   FreeChunk*  getChunkFromIndexedFreeListHelper(size_t size, bool replenish = true);
       
   260 
       
   261   // Get a chunk from the indexed free list.  If the indexed free list
       
   262   // does not have a free chunk, try to replenish the indexed free list
       
   263   // then get the free chunk from the replenished indexed free list.
       
   264   inline FreeChunk* getChunkFromIndexedFreeList(size_t size);
       
   265 
       
   266   // The returned chunk may be larger than requested (or null).
       
   267   FreeChunk* getChunkFromDictionary(size_t size);
       
   268   // The returned chunk is the exact size requested (or null).
       
   269   FreeChunk* getChunkFromDictionaryExact(size_t size);
       
   270 
       
   271   // Find a chunk in the indexed free list that is the best
       
   272   // fit for size "numWords".
       
   273   FreeChunk* bestFitSmall(size_t numWords);
       
   274   // For free list "fl" of chunks of size > numWords,
       
   275   // remove a chunk, split off a chunk of size numWords
       
   276   // and return it.  The split off remainder is returned to
       
   277   // the free lists.  The old name for getFromListGreater
       
   278   // was lookInListGreater.
       
   279   FreeChunk* getFromListGreater(AdaptiveFreeList<FreeChunk>* fl, size_t numWords);
       
   280   // Get a chunk in the indexed free list or dictionary,
       
   281   // by considering a larger chunk and splitting it.
       
   282   FreeChunk* getChunkFromGreater(size_t numWords);
       
   283   //  Verify that the given chunk is in the indexed free lists.
       
   284   bool verifyChunkInIndexedFreeLists(FreeChunk* fc) const;
       
   285   // Remove the specified chunk from the indexed free lists.
       
   286   void       removeChunkFromIndexedFreeList(FreeChunk* fc);
       
   287   // Remove the specified chunk from the dictionary.
       
   288   void       removeChunkFromDictionary(FreeChunk* fc);
       
   289   // Split a free chunk into a smaller free chunk of size "new_size".
       
   290   // Return the smaller free chunk and return the remainder to the
       
   291   // free lists.
       
   292   FreeChunk* splitChunkAndReturnRemainder(FreeChunk* chunk, size_t new_size);
       
   293   // Add a chunk to the free lists.
       
   294   void       addChunkToFreeLists(HeapWord* chunk, size_t size);
       
   295   // Add a chunk to the free lists, preferring to suffix it
       
   296   // to the last free chunk at end of space if possible, and
       
   297   // updating the block census stats as well as block offset table.
       
   298   // Take any locks as appropriate if we are multithreaded.
       
   299   void       addChunkToFreeListsAtEndRecordingStats(HeapWord* chunk, size_t size);
       
   300   // Add a free chunk to the indexed free lists.
       
   301   void       returnChunkToFreeList(FreeChunk* chunk);
       
   302   // Add a free chunk to the dictionary.
       
   303   void       returnChunkToDictionary(FreeChunk* chunk);
       
   304 
       
   305   // Functions for maintaining the linear allocation buffers (LinAB).
       
   306   // Repairing a linear allocation block refers to operations
       
   307   // performed on the remainder of a LinAB after an allocation
       
   308   // has been made from it.
       
   309   void       repairLinearAllocationBlocks();
       
   310   void       repairLinearAllocBlock(LinearAllocBlock* blk);
       
   311   void       refillLinearAllocBlock(LinearAllocBlock* blk);
       
   312   void       refillLinearAllocBlockIfNeeded(LinearAllocBlock* blk);
       
   313   void       refillLinearAllocBlocksIfNeeded();
       
   314 
       
   315   void       verify_objects_initialized() const;
       
   316 
       
   317   // Statistics reporting helper functions
       
   318   void       reportFreeListStatistics(const char* title) const;
       
   319   void       reportIndexedFreeListStatistics(outputStream* st) const;
       
   320   size_t     maxChunkSizeInIndexedFreeLists() const;
       
   321   size_t     numFreeBlocksInIndexedFreeLists() const;
       
   322   // Accessor
       
   323   HeapWord* unallocated_block() const {
       
   324     if (BlockOffsetArrayUseUnallocatedBlock) {
       
   325       HeapWord* ub = _bt.unallocated_block();
       
   326       assert(ub >= bottom() &&
       
   327              ub <= end(), "space invariant");
       
   328       return ub;
       
   329     } else {
       
   330       return end();
       
   331     }
       
   332   }
       
   333   void freed(HeapWord* start, size_t size) {
       
   334     _bt.freed(start, size);
       
   335   }
       
   336 
       
   337   // Auxiliary functions for scan_and_{forward,adjust_pointers,compact} support.
       
   338   // See comments for CompactibleSpace for more information.
       
   339   inline HeapWord* scan_limit() const {
       
   340     return end();
       
   341   }
       
   342 
       
   343   inline bool scanned_block_is_obj(const HeapWord* addr) const {
       
   344     return CompactibleFreeListSpace::block_is_obj(addr); // Avoid virtual call
       
   345   }
       
   346 
       
   347   inline size_t scanned_block_size(const HeapWord* addr) const {
       
   348     return CompactibleFreeListSpace::block_size(addr); // Avoid virtual call
       
   349   }
       
   350 
       
   351   inline size_t adjust_obj_size(size_t size) const {
       
   352     return adjustObjectSize(size);
       
   353   }
       
   354 
       
   355   inline size_t obj_size(const HeapWord* addr) const;
       
   356 
       
   357  protected:
       
   358   // Reset the indexed free list to its initial empty condition.
       
   359   void resetIndexedFreeListArray();
       
   360   // Reset to an initial state with a single free block described
       
   361   // by the MemRegion parameter.
       
   362   void reset(MemRegion mr);
       
   363   // Return the total number of words in the indexed free lists.
       
   364   size_t     totalSizeInIndexedFreeLists() const;
       
   365 
       
   366  public:
       
   367   // Constructor
       
   368   CompactibleFreeListSpace(BlockOffsetSharedArray* bs, MemRegion mr);
       
   369   // Accessors
       
   370   bool bestFitFirst() { return _fitStrategy == FreeBlockBestFitFirst; }
       
   371   AFLBinaryTreeDictionary* dictionary() const { return _dictionary; }
       
   372   HeapWord* nearLargestChunk() const { return _nearLargestChunk; }
       
   373   void set_nearLargestChunk(HeapWord* v) { _nearLargestChunk = v; }
       
   374 
       
   375   // Set CMS global values.
       
   376   static void set_cms_values();
       
   377 
       
   378   // Return the free chunk at the end of the space.  If no such
       
   379   // chunk exists, return NULL.
       
   380   FreeChunk* find_chunk_at_end();
       
   381 
       
   382   void set_collector(CMSCollector* collector) { _collector = collector; }
       
   383 
       
   384   // Support for parallelization of rescan and marking.
       
   385   const size_t rescan_task_size()  const { return _rescan_task_size;  }
       
   386   const size_t marking_task_size() const { return _marking_task_size; }
       
   387   // Return ergonomic max size for CMSRescanMultiple and CMSConcMarkMultiple.
       
   388   const size_t max_flag_size_for_task_size() const;
       
   389   SequentialSubTasksDone* conc_par_seq_tasks() {return &_conc_par_seq_tasks; }
       
   390   void initialize_sequential_subtasks_for_rescan(int n_threads);
       
   391   void initialize_sequential_subtasks_for_marking(int n_threads,
       
   392          HeapWord* low = NULL);
       
   393 
       
   394   virtual MemRegionClosure* preconsumptionDirtyCardClosure() const {
       
   395     return _preconsumptionDirtyCardClosure;
       
   396   }
       
   397 
       
   398   void setPreconsumptionDirtyCardClosure(MemRegionClosure* cl) {
       
   399     _preconsumptionDirtyCardClosure = cl;
       
   400   }
       
   401 
       
   402   // Space enquiries
       
   403   size_t used() const;
       
   404   size_t free() const;
       
   405   size_t max_alloc_in_words() const;
       
   406   // XXX: should have a less conservative used_region() than that of
       
   407   // Space; we could consider keeping track of highest allocated
       
   408   // address and correcting that at each sweep, as the sweeper
       
   409   // goes through the entire allocated part of the generation. We
       
   410   // could also use that information to keep the sweeper from
       
   411   // sweeping more than is necessary. The allocator and sweeper will
       
   412   // of course need to synchronize on this, since the sweeper will
       
   413   // try to bump down the address and the allocator will try to bump it up.
       
   414   // For now, however, we'll just use the default used_region()
       
   415   // which overestimates the region by returning the entire
       
   416   // committed region (this is safe, but inefficient).
       
   417 
       
   418   // Returns monotonically increasing stable used space bytes for CMS.
       
   419   // This is required for jstat and other memory monitoring tools
       
   420   // that might otherwise see inconsistent used space values during a garbage
       
   421   // collection, promotion or allocation into compactibleFreeListSpace.
       
   422   // The value returned by this function might be smaller than the
       
   423   // actual value.
       
   424   size_t used_stable() const;
       
   425   // Recalculate and cache the current stable used() value. Only to be called
       
   426   // in places where we can be sure that the result is stable.
       
   427   void recalculate_used_stable();
       
   428 
       
   429   // Returns a subregion of the space containing all the objects in
       
   430   // the space.
       
   431   MemRegion used_region() const {
       
   432     return MemRegion(bottom(),
       
   433                      BlockOffsetArrayUseUnallocatedBlock ?
       
   434                      unallocated_block() : end());
       
   435   }
       
   436 
       
   437   virtual bool is_free_block(const HeapWord* p) const;
       
   438 
       
   439   // Resizing support
       
   440   void set_end(HeapWord* value);  // override
       
   441 
       
   442   // Never mangle CompactibleFreeListSpace
       
   443   void mangle_unused_area() {}
       
   444   void mangle_unused_area_complete() {}
       
   445 
       
   446   // Mutual exclusion support
       
   447   Mutex* freelistLock() const { return &_freelistLock; }
       
   448 
       
   449   // Iteration support
       
   450   void oop_iterate(OopIterateClosure* cl);
       
   451 
       
   452   void object_iterate(ObjectClosure* blk);
       
   453   // Apply the closure to each object in the space whose references
       
   454   // point to objects in the heap.  The usage of CompactibleFreeListSpace
       
   455   // by the ConcurrentMarkSweepGeneration for concurrent GC's allows
       
   456   // objects in the space with references to objects that are no longer
       
   457   // valid.  For example, an object may reference another object
       
   458   // that has already been sweep up (collected).  This method uses
       
   459   // obj_is_alive() to determine whether it is safe to iterate of
       
   460   // an object.
       
   461   void safe_object_iterate(ObjectClosure* blk);
       
   462 
       
   463   // Iterate over all objects that intersect with mr, calling "cl->do_object"
       
   464   // on each.  There is an exception to this: if this closure has already
       
   465   // been invoked on an object, it may skip such objects in some cases.  This is
       
   466   // Most likely to happen in an "upwards" (ascending address) iteration of
       
   467   // MemRegions.
       
   468   void object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl);
       
   469 
       
   470   // Requires that "mr" be entirely within the space.
       
   471   // Apply "cl->do_object" to all objects that intersect with "mr".
       
   472   // If the iteration encounters an unparseable portion of the region,
       
   473   // terminate the iteration and return the address of the start of the
       
   474   // subregion that isn't done.  Return of "NULL" indicates that the
       
   475   // iteration completed.
       
   476   HeapWord* object_iterate_careful_m(MemRegion mr,
       
   477                                      ObjectClosureCareful* cl);
       
   478 
       
   479   // Override: provides a DCTO_CL specific to this kind of space.
       
   480   DirtyCardToOopClosure* new_dcto_cl(OopIterateClosure* cl,
       
   481                                      CardTable::PrecisionStyle precision,
       
   482                                      HeapWord* boundary,
       
   483                                      bool parallel);
       
   484 
       
   485   void blk_iterate(BlkClosure* cl);
       
   486   void blk_iterate_careful(BlkClosureCareful* cl);
       
   487   HeapWord* block_start_const(const void* p) const;
       
   488   HeapWord* block_start_careful(const void* p) const;
       
   489   size_t block_size(const HeapWord* p) const;
       
   490   size_t block_size_no_stall(HeapWord* p, const CMSCollector* c) const;
       
   491   bool block_is_obj(const HeapWord* p) const;
       
   492   bool obj_is_alive(const HeapWord* p) const;
       
   493   size_t block_size_nopar(const HeapWord* p) const;
       
   494   bool block_is_obj_nopar(const HeapWord* p) const;
       
   495 
       
   496   // Iteration support for promotion
       
   497   void save_marks();
       
   498   bool no_allocs_since_save_marks();
       
   499 
       
   500   // Iteration support for sweeping
       
   501   void save_sweep_limit() {
       
   502     _sweep_limit = BlockOffsetArrayUseUnallocatedBlock ?
       
   503                    unallocated_block() : end();
       
   504     log_develop_trace(gc, sweep)(">>>>> Saving sweep limit " PTR_FORMAT
       
   505                                  "  for space [" PTR_FORMAT "," PTR_FORMAT ") <<<<<<",
       
   506                                  p2i(_sweep_limit), p2i(bottom()), p2i(end()));
       
   507   }
       
   508   NOT_PRODUCT(
       
   509     void clear_sweep_limit() { _sweep_limit = NULL; }
       
   510   )
       
   511   HeapWord* sweep_limit() { return _sweep_limit; }
       
   512 
       
   513   // Apply "blk->do_oop" to the addresses of all reference fields in objects
       
   514   // promoted into this generation since the most recent save_marks() call.
       
   515   // Fields in objects allocated by applications of the closure
       
   516   // *are* included in the iteration. Thus, when the iteration completes
       
   517   // there should be no further such objects remaining.
       
   518   template <typename OopClosureType>
       
   519   void oop_since_save_marks_iterate(OopClosureType* blk);
       
   520 
       
   521   // Allocation support
       
   522   HeapWord* allocate(size_t size);
       
   523   HeapWord* par_allocate(size_t size);
       
   524 
       
   525   oop       promote(oop obj, size_t obj_size);
       
   526   void      gc_prologue();
       
   527   void      gc_epilogue();
       
   528 
       
   529   // This call is used by a containing CMS generation / collector
       
   530   // to inform the CFLS space that a sweep has been completed
       
   531   // and that the space can do any related house-keeping functions.
       
   532   void      sweep_completed();
       
   533 
       
   534   // For an object in this space, the mark-word's two
       
   535   // LSB's having the value [11] indicates that it has been
       
   536   // promoted since the most recent call to save_marks() on
       
   537   // this generation and has not subsequently been iterated
       
   538   // over (using oop_since_save_marks_iterate() above).
       
   539   // This property holds only for single-threaded collections,
       
   540   // and is typically used for Cheney scans; for MT scavenges,
       
   541   // the property holds for all objects promoted during that
       
   542   // scavenge for the duration of the scavenge and is used
       
   543   // by card-scanning to avoid scanning objects (being) promoted
       
   544   // during that scavenge.
       
   545   bool obj_allocated_since_save_marks(const oop obj) const {
       
   546     assert(is_in_reserved(obj), "Wrong space?");
       
   547     return ((PromotedObject*)obj)->hasPromotedMark();
       
   548   }
       
   549 
       
   550   // A worst-case estimate of the space required (in HeapWords) to expand the
       
   551   // heap when promoting an obj of size obj_size.
       
   552   size_t expansionSpaceRequired(size_t obj_size) const;
       
   553 
       
   554   FreeChunk* allocateScratch(size_t size);
       
   555 
       
   556   // Returns true if either the small or large linear allocation buffer is empty.
       
   557   bool       linearAllocationWouldFail() const;
       
   558 
       
   559   // Adjust the chunk for the minimum size.  This version is called in
       
   560   // most cases in CompactibleFreeListSpace methods.
       
   561   inline static size_t adjustObjectSize(size_t size) {
       
   562     return align_object_size(MAX2(size, (size_t)MinChunkSize));
       
   563   }
       
   564   // This is a virtual version of adjustObjectSize() that is called
       
   565   // only occasionally when the compaction space changes and the type
       
   566   // of the new compaction space is is only known to be CompactibleSpace.
       
   567   size_t adjust_object_size_v(size_t size) const {
       
   568     return adjustObjectSize(size);
       
   569   }
       
   570   // Minimum size of a free block.
       
   571   virtual size_t minimum_free_block_size() const { return MinChunkSize; }
       
   572   void      removeFreeChunkFromFreeLists(FreeChunk* chunk);
       
   573   void      addChunkAndRepairOffsetTable(HeapWord* chunk, size_t size,
       
   574               bool coalesced);
       
   575 
       
   576   // Support for compaction.
       
   577   void prepare_for_compaction(CompactPoint* cp);
       
   578   void adjust_pointers();
       
   579   void compact();
       
   580   // Reset the space to reflect the fact that a compaction of the
       
   581   // space has been done.
       
   582   virtual void reset_after_compaction();
       
   583 
       
   584   // Debugging support.
       
   585   void print()                            const;
       
   586   void print_on(outputStream* st)         const;
       
   587   void prepare_for_verify();
       
   588   void verify()                           const;
       
   589   void verifyFreeLists()                  const PRODUCT_RETURN;
       
   590   void verifyIndexedFreeLists()           const;
       
   591   void verifyIndexedFreeList(size_t size) const;
       
   592   // Verify that the given chunk is in the free lists:
       
   593   // i.e. either the binary tree dictionary, the indexed free lists
       
   594   // or the linear allocation block.
       
   595   bool verify_chunk_in_free_list(FreeChunk* fc) const;
       
   596   // Verify that the given chunk is the linear allocation block.
       
   597   bool verify_chunk_is_linear_alloc_block(FreeChunk* fc) const;
       
   598   // Do some basic checks on the the free lists.
       
   599   void check_free_list_consistency()      const PRODUCT_RETURN;
       
   600 
       
   601   // Printing support
       
   602   void dump_at_safepoint_with_locks(CMSCollector* c, outputStream* st);
       
   603   void print_indexed_free_lists(outputStream* st) const;
       
   604   void print_dictionary_free_lists(outputStream* st) const;
       
   605   void print_promo_info_blocks(outputStream* st) const;
       
   606 
       
   607   NOT_PRODUCT (
       
   608     void initializeIndexedFreeListArrayReturnedBytes();
       
   609     size_t sumIndexedFreeListArrayReturnedBytes();
       
   610     // Return the total number of chunks in the indexed free lists.
       
   611     size_t totalCountInIndexedFreeLists() const;
       
   612     // Return the total number of chunks in the space.
       
   613     size_t totalCount();
       
   614   )
       
   615 
       
   616   // The census consists of counts of the quantities such as
       
   617   // the current count of the free chunks, number of chunks
       
   618   // created as a result of the split of a larger chunk or
       
   619   // coalescing of smaller chucks, etc.  The counts in the
       
   620   // census is used to make decisions on splitting and
       
   621   // coalescing of chunks during the sweep of garbage.
       
   622 
       
   623   // Print the statistics for the free lists.
       
   624   void printFLCensus(size_t sweep_count) const;
       
   625 
       
   626   // Statistics functions
       
   627   // Initialize census for lists before the sweep.
       
   628   void beginSweepFLCensus(float inter_sweep_current,
       
   629                           float inter_sweep_estimate,
       
   630                           float intra_sweep_estimate);
       
   631   // Set the surplus for each of the free lists.
       
   632   void setFLSurplus();
       
   633   // Set the hint for each of the free lists.
       
   634   void setFLHints();
       
   635   // Clear the census for each of the free lists.
       
   636   void clearFLCensus();
       
   637   // Perform functions for the census after the end of the sweep.
       
   638   void endSweepFLCensus(size_t sweep_count);
       
   639   // Return true if the count of free chunks is greater
       
   640   // than the desired number of free chunks.
       
   641   bool coalOverPopulated(size_t size);
       
   642 
       
   643 // Record (for each size):
       
   644 //
       
   645 //   split-births = #chunks added due to splits in (prev-sweep-end,
       
   646 //      this-sweep-start)
       
   647 //   split-deaths = #chunks removed for splits in (prev-sweep-end,
       
   648 //      this-sweep-start)
       
   649 //   num-curr     = #chunks at start of this sweep
       
   650 //   num-prev     = #chunks at end of previous sweep
       
   651 //
       
   652 // The above are quantities that are measured. Now define:
       
   653 //
       
   654 //   num-desired := num-prev + split-births - split-deaths - num-curr
       
   655 //
       
   656 // Roughly, num-prev + split-births is the supply,
       
   657 // split-deaths is demand due to other sizes
       
   658 // and num-curr is what we have left.
       
   659 //
       
   660 // Thus, num-desired is roughly speaking the "legitimate demand"
       
   661 // for blocks of this size and what we are striving to reach at the
       
   662 // end of the current sweep.
       
   663 //
       
   664 // For a given list, let num-len be its current population.
       
   665 // Define, for a free list of a given size:
       
   666 //
       
   667 //   coal-overpopulated := num-len >= num-desired * coal-surplus
       
   668 // (coal-surplus is set to 1.05, i.e. we allow a little slop when
       
   669 // coalescing -- we do not coalesce unless we think that the current
       
   670 // supply has exceeded the estimated demand by more than 5%).
       
   671 //
       
   672 // For the set of sizes in the binary tree, which is neither dense nor
       
   673 // closed, it may be the case that for a particular size we have never
       
   674 // had, or do not now have, or did not have at the previous sweep,
       
   675 // chunks of that size. We need to extend the definition of
       
   676 // coal-overpopulated to such sizes as well:
       
   677 //
       
   678 //   For a chunk in/not in the binary tree, extend coal-overpopulated
       
   679 //   defined above to include all sizes as follows:
       
   680 //
       
   681 //   . a size that is non-existent is coal-overpopulated
       
   682 //   . a size that has a num-desired <= 0 as defined above is
       
   683 //     coal-overpopulated.
       
   684 //
       
   685 // Also define, for a chunk heap-offset C and mountain heap-offset M:
       
   686 //
       
   687 //   close-to-mountain := C >= 0.99 * M
       
   688 //
       
   689 // Now, the coalescing strategy is:
       
   690 //
       
   691 //    Coalesce left-hand chunk with right-hand chunk if and
       
   692 //    only if:
       
   693 //
       
   694 //      EITHER
       
   695 //        . left-hand chunk is of a size that is coal-overpopulated
       
   696 //      OR
       
   697 //        . right-hand chunk is close-to-mountain
       
   698   void smallCoalBirth(size_t size);
       
   699   void smallCoalDeath(size_t size);
       
   700   void coalBirth(size_t size);
       
   701   void coalDeath(size_t size);
       
   702   void smallSplitBirth(size_t size);
       
   703   void smallSplitDeath(size_t size);
       
   704   void split_birth(size_t size);
       
   705   void splitDeath(size_t size);
       
   706   void split(size_t from, size_t to1);
       
   707 
       
   708   double flsFrag() const;
       
   709 };
       
   710 
       
   711 // A parallel-GC-thread-local allocation buffer for allocation into a
       
   712 // CompactibleFreeListSpace.
       
   713 class CompactibleFreeListSpaceLAB : public CHeapObj<mtGC> {
       
   714   // The space that this buffer allocates into.
       
   715   CompactibleFreeListSpace* _cfls;
       
   716 
       
   717   // Our local free lists.
       
   718   AdaptiveFreeList<FreeChunk> _indexedFreeList[CompactibleFreeListSpace::IndexSetSize];
       
   719 
       
   720   // Initialized from a command-line arg.
       
   721 
       
   722   // Allocation statistics in support of dynamic adjustment of
       
   723   // #blocks to claim per get_from_global_pool() call below.
       
   724   static AdaptiveWeightedAverage
       
   725                  _blocks_to_claim  [CompactibleFreeListSpace::IndexSetSize];
       
   726   static size_t _global_num_blocks [CompactibleFreeListSpace::IndexSetSize];
       
   727   static uint   _global_num_workers[CompactibleFreeListSpace::IndexSetSize];
       
   728   size_t        _num_blocks        [CompactibleFreeListSpace::IndexSetSize];
       
   729 
       
   730   // Internal work method
       
   731   void get_from_global_pool(size_t word_sz, AdaptiveFreeList<FreeChunk>* fl);
       
   732 
       
   733 public:
       
   734   static const int _default_dynamic_old_plab_size = 16;
       
   735   static const int _default_static_old_plab_size  = 50;
       
   736 
       
   737   CompactibleFreeListSpaceLAB(CompactibleFreeListSpace* cfls);
       
   738 
       
   739   // Allocate and return a block of the given size, or else return NULL.
       
   740   HeapWord* alloc(size_t word_sz);
       
   741 
       
   742   // Return any unused portions of the buffer to the global pool.
       
   743   void retire(int tid);
       
   744 
       
   745   // Dynamic OldPLABSize sizing
       
   746   static void compute_desired_plab_size();
       
   747   // When the settings are modified from default static initialization
       
   748   static void modify_initialization(size_t n, unsigned wt);
       
   749 };
       
   750 
       
   751 size_t PromotionInfo::refillSize() const {
       
   752   const size_t CMSSpoolBlockSize = 256;
       
   753   const size_t sz = heap_word_size(sizeof(SpoolBlock) + sizeof(markWord)
       
   754                                    * CMSSpoolBlockSize);
       
   755   return CompactibleFreeListSpace::adjustObjectSize(sz);
       
   756 }
       
   757 
       
   758 #endif // SHARE_GC_CMS_COMPACTIBLEFREELISTSPACE_HPP